Shielding Structures Including Frequency Selective Surfaces

ABSTRACT

According to various aspects, exemplary embodiments are disclosed of shielding structures including one or more frequency selective surfaces, which may be used for attenuating, reflecting, and/or redirecting electromagnetic signals through open structures. Also disclosed are methods of using one or more frequency selective surfaces for attenuating, reflecting, and/or redirecting electromagnetic signals through open structures.

FIELD

The present disclosure relates to shielding structures includingfrequency selective surfaces, which may be used for attenuatingelectromagnetic signals through open or closed structures.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

The operation of electronic devices generates electromagnetic radiationwithin the electronic circuitry of the equipment. Such radiation mayresult in electromagnetic interference (EMI) or radio frequencyinterference (RFI), which can interfere with the operation of otherelectronic devices within a certain proximity. Without adequateshielding, EMI/RFI interference may cause degradation or complete lossof important signals, thereby rendering the electronic equipmentinefficient or inoperable.

A common solution to ameliorate the effects of EMI/RFI is through theuse of shields capable of absorbing and/or reflecting and/or redirectingEMI energy. These shields are typically employed to localize EMI/RFIwithin its source, and to insulate other devices proximal to the EMI/RFIsource.

The term “EMI” as used herein should be considered to generally includeand refer to EMI emissions and RFI emissions, and the term“electromagnetic” should be considered to generally include and refer toelectromagnetic and radio frequency from external sources and internalsources. Accordingly, the term shielding (as used herein) broadlyincludes and refers to mitigating (or limiting) EMI and/or RFI, such asby absorbing, reflecting, blocking, and/or redirecting the energy orsome combination thereof so that it no longer interferes, for example,for government compliance and/or for internal functionality of theelectronic component system.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to various aspects, exemplary embodiments are disclosed ofshielding structures including one or more frequency selective surfaces,which may be used for attenuating, reflecting, and/or redirectingelectromagnetic signals through open structures. Also disclosed aremethods of using one or more frequency selective surfaces forattenuating, reflecting, and/or redirecting electromagnetic signalsthrough open structures.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 illustrates a printed circuit board (PCB) having an integratedcircuit, a frequency selective surface/period structure within the PCB,and a frequency selective surface/period structure applied or disposedover the integrated circuit whereby the frequency selective surfaces areoperable for providing shielding to the integrated circuit according toexemplary embodiments.

FIG. 2 illustrates an exemplary embodiment of a frequency selectivesurface that may be used as a single band or multiband bandstopwaveguide and/or shielding structure, where the frequency selectivesurface may include any suitable number of suitably configured (e.g.,shaped and sized, etc.) electrically-conductive, electromagnetic energyabsorbing, and/or magnetic members (e.g., rings and/or otherconfigurations, etc.) as represented by the series of dots.

FIG. 3 illustrates an exemplary embodiment of a frequency selectivesurface that may be used as a single band or multiband bandstopwaveguide and/or shielding structure, where the frequency selectivesurface includes electromagnetic energy absorptive material applied toelectrically-conductive material, which is within dielectric material.

FIG. 4 illustrates an exemplary embodiment of a frequency selectivesurface that may be used as a single band or multiband bandstopwaveguide and/or shielding structure, where the frequency selectivesurface includes a dielectric and electrically-conductive material on asurface of the dielectric.

FIG. 5 illustrates an exemplary embodiment of a frequency selectivesurface that may be used as a single band or multiband bandstopwaveguide and/or shielding structure, where the frequency selectivesurface includes a dielectric and electromagnetic energy absorptivematerial on a surface of the dielectric.

FIG. 6 illustrates an exemplary embodiment of a frequency selectivesurface that may be used as a single band or multiband bandstopwaveguide and/or shielding structure, where the frequency selectivesurface includes a dielectric and electromagnetic energy absorptivematerial applied to electrically-conductive material on a surface of thedielectric.

FIG. 7 illustrates an exemplary embodiment of a frequency selectivesurface having dielectric members and electrically-conductive ringssupported by and spaced apart from each other at specific locations bythe dielectric members, where the frequency selective surface is shownwithin a test fixture on a microstrip line for an MSL test for which theresults are shown in FIG. 8.

FIG. 8 is an exemplary line graph showing signal strength in decibels(dB) versus frequency in gigahertz (GHz) for first and second tests(referred to as S21 and MSL tests) in which reference signals betweentwo antennas pointed at each other were recorded with and without anexemplary embodiment of a frequency selective surface therebetween toshow bandstop capabilities of the frequency selective surface.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

As explained above in the background, shields are commonly used toameliorate the effects of EMI/RFI by absorbing and/or reflecting and/orredirecting EMI energy. Traditional shielding methods and materials relyon an electrically conductive surface completely enclosing a source ofelectromagnetic radiation. In reality, however, some gaps in theelectrically conductive surface must remain to allow instrument egressand to allow airflow, which gaps will allow signal leakage.Electromagnetic absorbent material may be used to attenuate the signalleakage through a gap. But the absorber must completely cover the gap inorder to be effective. In which case, the absorber inhibits or preventsequipment access or airflow, which is often not feasible as sometimesequipment access and/or or airflow must be maintained.

After recognizing the above, the inventors developed the disclosedexemplary embodiments of single band or multiband bandstop waveguideand/or shielding structures using or including one or more frequencyselective surfaces/periodic structures. Also disclosed herein areexemplary methods for attenuating electromagnetic signals through openor closed structures by using one or more frequency selectivesurfaces/periodic structures. The inventors have recognized theadvantages in using frequency selective surfaces for shielding purposesin that frequency selective surfaces may be installed within openstructures for attenuating (e.g., reflecting, blocking, redirecting,and/or absorbing, etc.) electromagnetic signals through the openstructures without preventing objects and airflow to pass through theopen structures.

A frequency selective surface is a passive electromagnetic sheet that isdesigned to block, reflect, absorb, and/or redirect electromagneticenergy over one or more specific frequency bands usingelectrically-conductive and/or electromagnetic energy absorbing materialin patterns, which may be located on a dielectric substrate. Thebandstop properties exist even at very large angles of incidence, e.g.,glancing or grazing angles at which the electromagnetic signals aretraveling nearly parallel to the frequency selective surface. Asdisclosed herein, exemplary embodiments are disclosed in which one ormore frequency selective surfaces are operable for reflecting, blocking,redirecting, and/or absorbing electromagnetic signals which propagatethrough a channel, waveguide structure, vent panel, or other openstructure, while still allowing egress of equipment and/or the passageof airflow.

With reference now to the figures, FIG. 1 illustrates an exemplaryembodiment including a single band or multiband bandstop waveguideand/or shielding structure embodying one or more aspects of the presentdisclosure. This illustrated embodiment comprises first and secondfrequency selective surfaces or periodic structures 104, 108 operablefor providing shielding for an integrated circuited 112 on a printedcircuit board (PCB) 116. The first frequency selective surface 104 iswithin the PCB 116. The second frequency selective surface 108 ispositioned, applied, or disposed over the integrated circuit 112. Thefrequency selective surfaces 104, 108 are operable for attenuating(e.g., reflecting, blocking, redirecting, and/or absorbing, etc.)electromagnetic signals to/from the integrated circuit 112.

The frequency selective surfaces 104, 108 includeelectrically-conductive and/or electromagnetic energy absorbing materialor members in the same or different pattern (e.g., spaced apartelectrically-conductive rings, etc.) for blocking, reflecting,redirecting, and/or absorbing electromagnetic energy over one or morespecific frequency bands. The electrically-conductive and/orelectromagnetic energy absorbing material may be in a pattern relativeto a dielectric (e.g., a dielectric substrate, air, etc.). For example,the electrically-conductive and/or electromagnetic energy absorbingmaterial may be on a top and/or bottom surface of a dielectric substrateand/or within the dielectric substrate. As another example, dielectricmembers may support, suspend, and/or retain electrically-conductiveand/or electromagnetic energy absorbing members at spaced apartlocations from each other in a pattern. In this example, the frequencyselective surface may not include any dielectric substrate as theelectrically-conductive and/or electromagnetic energy absorbing membersmay instead be suspended, e.g., in air, by the dielectric members.

In exemplary embodiments that include more than one frequency selectivesurface, the frequency selective surfaces may be identical to each otheror different from each other. In addition, a frequency selective surfacemay include any suitable number of electrically-conductive and/orelectromagnetic energy absorbing members that all have the sameconfiguration (e.g., same shape, same size, same pattern, etc.) or thatdo not all have the same configuration (e.g., different shape, differentsize, different pattern, etc.). For example, a frequency selectivesurface may have electrically-conductive and/or electromagnetic energyabsorbing members that are shaped differently and/or sized differentlyto work at multiple frequencies and/or over a broader bandwidth.

In some exemplary embodiments, a frequency selective surface may haveelectromagnetic energy absorbing material(s) or absorber(s) on orcoupled to electrically-conductive material(s) or conductor(s), such asshown in FIGS. 2, 3, and 6. For example, an electromagnetic energyabsorbing material(s) or absorber(s) may be stacked on top of theelectrically-conductive material(s) or conductor(s). Or, for example, anelectromagnetic energy absorbing thin film(s) may be disposed over andattached to the electrically-conductive material(s) or conductor(s). Asyet another example, the electrically-conductive material(s) orconductor(s) may be coated with one or more electromagnetic energyabsorbing coatings. In other exemplary embodiments, a frequencyselective surface includes only electromagnetic energy absorbingmaterial(s) or absorber(s) only (e.g., FIG. 5, etc.) or onlyelectrically-conductive material(s) or conductor(s) (e.g., FIG. 4,etc.). In still other exemplary embodiments, a frequency selectivesurface includes electromagnetic energy absorbing material(s) orabsorber(s) that are adjacent or alongside, but not stacked on top of,the electrically-conductive material(s) or conductor(s).

The illustrated embodiment of FIG. 1 includes the first and secondfrequency selective surfaces 104, 108, which are respectively within thePCB 116 and disposed over the integrated circuit 112. Alternativeexemplary embodiments may include more or less than two frequencyselective surfaces. For example, other exemplary embodiments includeeither a first frequency selective surface within a PCB substrate or asecond frequency selective surface disposed over an integrated circuiton the PCB, but not both. Additional exemplary embodiments include afrequency selective surface on the top surface and/or bottom surface ofthe PCB substrate, without any frequency selective surface within thePCB substrate or disposed over an integrated circuit on the substrate.Further exemplary embodiments include more than two frequency selectivesurfaces, such as a first frequency selective surface within the PCBsubstrate, a second frequency selective surface disposed over anintegrated circuit on the PCB, and a third frequency selective surfaceon the top or bottom surface of the PCB substrate. Still furtherexemplary embodiments include a first frequency selective surface withinthe PCB substrate, a second frequency selective surface disposed over anintegrated circuit on the PCB, a third frequency selective surface onthe top surface of the PCB substrate, and a fourth frequency selectivesurface on the bottom surface of the PCB substrate. Additionally, oralternatively, a frequency selective surface may placed on anothersurface in the vicinity of an EMI noise path instead of, or in additionto, placement of a frequency selective surface on a circuit, within aPCB, and/or on a surface of a PCB (e.g., underneath, etc.).

FIG. 2 illustrates an exemplary embodiment of a frequency selectivesurface or periodic structure 204 that may be used as a single band ormultiband bandstop waveguide and/or shielding structure. As representedby the series of dots and distance (d) in FIG. 2, the frequencyselective surface 204 (and other frequency selective surfaces disclosedherein) may include any suitable number of suitably configured (e.g.,shaped, sized, spaced apart, patterned, etc.) electrically-conductiveand/or electromagnetic energy absorbing members (e.g., rings and/orother shapes, etc.) depending, for example, on what frequency orfrequencies are to be reflected, absorbed, blocked, and/or redirected bythe frequency selective surface 204. The frequency selective surface 204may be designed, configured, or tuned to reflect, absorb, block, and/orredirect energy at one or more desired frequencies or frequencybandwidths (e.g., about 9 Gigahertz, etc.).

In this example, the frequency selective surface 204 includeselectrically-conductive material or conductors 220 and electromagneticenergy absorbing material or absorbers 224 on or applied to theelectrically-conductive material or conductors 220. FIG. 2 alsoillustrates a dielectric 228, which may comprise any suitable dielectricincluding dielectric substrate materials, air, etc. In operation, thefrequency selective surface 204 reflects, absorbs, blocks, and/orredirects signals at near glancing incidence (90 degrees off normal) tostop energy while also allowing other objects and airflow through.

FIG. 3 illustrates an exemplary embodiment of a frequency selectivesurface 304 that may be used as a single band or multiband bandstopwaveguide and/or shielding structure. As shown in FIG. 3, anelectromagnetic energy absorptive material or absorber 324 is on orapplied to electrically-conductive material or electrical conductor 320.During use, the electromagnetic energy absorbing material 324 isoperable for attenuating or absorbing electromagnetic signals reflectedby the frequency selective surface 304. Although FIG. 3 only illustratesa single electrical conductor 320 and single absorber 324 thereon, thefrequency selective surface 304 may include any suitable number ofsuitably configured (e.g., shaped, sized, spaced apart, patterned, etc.)electrical conductors 320 and absorbers 324 (e.g., rings and/or othershapes, etc.) depending, for example, on what frequency or frequenciesare to be reflected by the frequency selective surface 304.

FIG. 3 also illustrates dielectrics 328 and 332. The dielectrics 328,332 may comprise portions of the same dielectric, e.g., upper and lowerportions of the same dielectric substrate. Or the dielectrics 328, 332may comprise different dielectrics. For example, the dielectric 328 maybe a dielectric substrate while the dielectric 332 may comprise air.

FIG. 4 illustrates an exemplary embodiment of a frequency selectivesurface 404 that may be used as a single band or multiband bandstopwaveguide and/or shielding structure. As shown in FIG. 4, the frequencyselective surface 404 includes an electrically-conductive material orelectrical conductor 420 on a surface of a dielectric 428. Although FIG.4 only illustrates a single electrical conductor 420, the frequencyselective surface 404 may include any suitable number of suitablyconfigured (e.g., shaped, sized, spaced apart, patterned, etc.)electrical conductors depending, for example, on what frequency orfrequencies are to be reflected by the frequency selective surface 404.

FIG. 5 illustrates an exemplary embodiment of a frequency selectivesurface 504 that may be used as a single band or multiband bandstopwaveguide and/or shielding structure. As shown in FIG. 5, the frequencyselective surface 504 includes an electromagnetic energy absorptivematerial or absorber 520 on a surface of a dielectric 528. Although FIG.5 only illustrates a single absorber 520, the frequency selectivesurface 504 may include any suitable number of suitably configured(e.g., shaped, sized, spaced apart, patterned, etc.) absorbers 520depending, for example, on what frequency or frequencies are to bereflected by the frequency selective surface 504.

FIG. 6 illustrates an exemplary embodiment of a frequency selectivesurface 604 that may be used as a single band or multiband bandstopwaveguide and/or shielding structure. As shown in FIG. 6, the frequencyselective surface 604 includes an electromagnetic energy absorptivematerial or absorber 624 on or applied to an electrically-conductivematerial or conductor 620, which, in turn, is on a surface of adielectric 628. In an alternative embodiment, the positioning of theelectromagnetic energy absorptive material or absorber 624 andelectrically-conductive material or conductor 620 may be reversed, suchthat the electrically-conductive material or conductor 620 is on orapplied to an electromagnetic energy absorptive material or absorber624. Although FIG. 6 only illustrates a single electrical conductor 620and single absorber 624 thereon, the frequency selective surface 604 mayinclude any suitable number of suitably configured (e.g., shaped, sized,spaced apart, patterned, etc.) electrical conductors 620 and absorbers624 (e.g., rings and/or other shapes, etc.) depending, for example, onwhat frequency or frequencies are to be reflected by the frequencyselective surface 604.

FIG. 7 illustrates an example frequency selective surface 704 within atest fixture 732 and placed on a microstrip line 736 for MSL testingwhere the results are shown in FIG. 8 and described below. As shown inFIG. 7, the frequency selective surface 704 includes a plurality ofelectrically-conductive and/or electromagnetic energy absorptive membersand a plurality of dielectric members, struts, or spacers 740. Thedielectric members 740 are connected to and extend between pairs ofelectrically-conductive and/or electromagnetic energy absorptive members720. In this example, the frequency selective surface 704 does notinclude a dielectric substrate as the electrically-conductive membersand/or electromagnetic energy absorbing members 720 are insteadsuspended, e.g., in air, and held in place by the dielectric members740.

In this illustrated embodiment, the electrically-conductive membersand/or electromagnetic energy absorbing members 720 are circular rings.The plurality of dielectric members 740 are linear or straight memberseach of which is connected between a corresponding pair of theelectrically-conductive and/or electromagnetic energy absorptive rings.The electrically-conductive members and/or electromagnetic energyabsorbing members 720 are at the vertices of equilateral trianglesdefined by the dielectric members 740.

Continuing with this example shown in FIG. 7, theelectrically-conductive members and/or electromagnetic energy absorbingmembers 720 may have a ring inner diameter of about 10.2 millimeters(mm) and a ring outer diameter of about 12 mm. The centers of the ringsmay be separated by about 17.5 mm in a hexagonal pattern. Any threeadjacent rings form an equilateral triangle with sides equal to about17.5 mm. The thickness may be about 1 mm. The dimensions provided inthis paragraph are examples only.

The configuration shown in FIG. 7 is but one example of a possiblefrequency selective surface that may be used in an exemplary embodimentas other exemplary embodiments may include one or more frequencyselective surfaces tuned to different frequencies by varying the shape,size, distance of separation, overall geometric layout, etc. of thedielectric members and/or of the electrically-conductive and/orelectromagnetic energy absorbing members. Other layouts or geometriesmay be used for the frequency selective surface 704, such aselectrically-conductive and/or electromagnetic energy absorptive membersin a greater or lesser number, that are spaced apart differently (e.g.,closer or farther away from each other), and/or that have differentshapes, etc. For example, the electrically-conductive and/orelectromagnetic energy absorbing members 720 may be non-circular, e.g.,triangular, rectangular, pentagonal, hexagonal, spirals, crosses, etc.In addition, the dielectric members 740 may be non-linear and/orarranged differently to define other shapes besides the equilateraltriangles or hexagonal patterns shown in FIG. 7.

FIG. 8 is an exemplary line graph showing signal strength in decibels(dB) versus frequency in gigahertz (GHz) for two different tests. Duringthe two tests, reference signals between two antennas pointed at eachother was measured or recorded with and without an exemplary embodimentof a frequency selective surface therebetween. The results show bandstopcapabilities of the frequency selective surface. These test resultsshown in FIG. 8 are provided only for purposes of illustration and notfor purposes of limitation.

For the first test (called S21), the reference signal was measured orrecorded between two antennas pointed at each other. Then, a frequencyselective surface was inserted or positioned between the two antennas,and the reference signal is measured or recorded again. In FIG. 8, theS21 test results represent the measurements taken when the frequencyselective surface was between the two antennas.

Generally, the S21 test results show that the frequency selectivesurface blocks, reflects, redirects, and/or absorbs energy atfrequencies around 9 GHz. The level of band stoppage was better than 30dB, which means the signal that got through was at 1/1000th the level ofthe reference signal. These test results show that this exemplaryembodiment including the frequency selective surface had significantbandstop capabilities at around 9 GHz. Although FIG. 8 shows that thisexample embodiment including the frequency selective surface blocksenergy at frequencies around 9 GHz, other exemplary embodiments mayinclude one or more frequency selective surfaces that are tuned to stopenergy at other suitable frequency or frequencies.

The second test (called microstrip line (MSL) test) is performed on amicrostrip line. The reference measurement is taken with an emptyfixture. Then, a frequency selective surface 704 is placed on the upperconductor of the microstrip line 736 as shown in FIG. 7 and the signalis measured. The MSL test results in FIG. 8 show significant bandstopcapabilities (e.g., level of band stoppage more than 25 dB) at around 8GHz. Generally, the MSL test may be more indicative of the bandstopcapabilities of a bandstop waveguide and/or shielding structureincluding a frequency selective surface. This is because the signaltravels parallel to the frequency selective surface during the MSLtesting, and the electric and magnetic fields are perpendicular to thesurface or plane of the frequency selective surface. In comparison, theenergy is traveling perpendicular to the surface of the frequencyselective surface during the S21 testing, and the electric and magneticfields are parallel to the surface of the frequency selective surface.

A wide range of materials may be used for the electrically-conductivemembers or electrical conductors (e.g., 220, 320, 420, 620, 720, etc.)in exemplary embodiments that include electrically-conductive members orelectrical conductors. Example materials include metals (e.g., copper,nickel/copper, silver, etc.), electrically-conductive compositematerials, etc. Some exemplary embodiments includeelectrically-conductive members or electrical conductors comprisingelectrically-conductive pressure sensitive adhesive, such as anelectrically-conductive pressure sensitive adhesive available from LairdTechnologies, Inc. By way of example only, an exemplary embodimentincludes one or more frequency selective surfaces havingelectrically-conductive members made of Laird Technologies' blackconductive fabric tape 86250 tape, which is a nickel/copper metallizedfabric with an electrically-conductive pressure sensitive adhesive. Byway of further example, another exemplary embodiment includes one ormore frequency selective surfaces having electrically-conductive and/orelectromagnetic energy absorptive members made of a correspondingelectrically-conductive and/or electromagnetic energy absorptivepressure sensitive adhesive.

A wide range of dielectrics may also be used in exemplary embodimentsdisclosed herein. For example, the dielectric members (e.g., 740 (inFIG. 7) etc.) connected to electrically-conductive and/orelectromagnetic energy absorptive members (e.g., 720, etc.) in exemplaryembodiments may be made of plastics (e.g., acrylonitrile butadienestyrene (ABS) plastic, etc.), electrically non-conductive pressuresensitive adhesives, etc. In an exemplary embodiment, the dielectricmembers 740 are made of ABS plastic. In another exemplary embodiment,the dielectric members 740 are made of electrically non-conductive ordielectric pressure sensitive adhesive.

A wide range of materials may be used for a dielectric substrate (e.g.,228, 328, 428, 528, 628, etc.) in exemplary embodiments disclosedherein, such as plastics (e.g., ABS plastic, Mylar plastic, etc.),composite materials (e.g., FR4 composite material, etc.), flexible,and/or thermally conductive materials. An exemplary embodiment includesa frequency selective surface having a substrate comprising ABS plastic.Another exemplary embodiment includes a frequency selective surfacehaving a substrate comprising FR4 composite material, which includeswoven fiberglass cloth with an epoxy resin binder that is flameresistant.

In some exemplary embodiments, a frequency selective surface may bethermally conductive (e.g., have a thermal conductivity greater thanair, have a thermal conductivity greater than 0.5 Watts per meter perKelvin (w/mK), etc.) and/or flexible. By way of example, an exemplaryembodiment includes a frequency selective surface having sufficientflexibility to allow it to be applied to virtually any part of a deviceeven after the device has been designed and manufactured. For example, afrequency selective surface may be applied to or over an electroniccomponent on a PCB post-manufacture or after the PCB and electroniccomponent are manufactured.

In an exemplary embodiment, a flexible frequency selective surfaceincludes electrically non-conductive or dielectric members and/or asubstrate comprising ABS plastic. Also in this exemplary embodiment, thefrequency selective surface includes electrically-conductive memberscomprising electrically-conductive pressure sensitive adhesive (e.g.,Laird Technologies' black conductive fabric tape 86250 tape, etc.). Inanother exemplary embodiment, a flexible frequency selective surfaceincludes electrically-conductive members comprising copper and asubstrate comprising Mylar. In this example, the copper pattern isetched onto the Mylar using FR4/PCB manufacturing processes, which hasthe advantage of being thinner and perhaps easier to manufacture.

In some exemplary embodiments, a frequency selective surface includeselectromagnetic energy absorptive material. During use, theelectromagnetically absorptive material is operable for attenuating theelectromagnetic signals reflected by the frequency selective surface. Awide range of electromagnetic energy absorptive materials may be used insome exemplary embodiments (e.g., FIG. 2, FIG. 3, FIG. 5, FIG. 6, etc.),including absorbing particles, fillers, flakes, etc. and/or made ofvarious electrically conductive and/or magnetic materials, such ascarbonyl iron, SENDUST (an alloy containing about 85% iron, 9.5% siliconand 5.5% aluminum), permalloy (an alloy containing about 20% iron and80% nickel), iron silicide, iron-chrome compounds, metallic silver,magnetic alloys, magnetic powders, magnetic flakes, magnetic particles,nickel-based alloys and powders, chrome alloys, and any combinationsthereof, etc. By way of example only, an exemplary embodiment of afrequency selective surface may include an electromagnetic energyabsorptive material available from Laird Technologies, Inc. and/or asdisclosed in U.S. Pat. No. 7,135,643, the entire contents of which isincorporated herein. As disclosed herein, exemplary embodiments mayinclude electrically-conductive members or electromagnetic energyabsorptive members. Additional exemplary embodiments may also includeboth electrically-conductive members and electromagnetic energyabsorptive members, which are in a stacked arrangement (e.g.,electromagnetic energy absorptive members are stacked onelectrically-conductive members, or vice versa, etc.) are adjacent orabutting one another. Other exemplary embodiments may include membersthat are configured to be electrically-conductive and electromagneticenergy absorptive.

In some exemplary embodiments, a frequency selective surface may includea thermally conductive, electromagnetic energy absorptive material. Inwhich case, the thermally conductive, electromagnetic energy absorptivematerial may be operable for attenuating the electromagnetic signalsreflected by the frequency selective surface while also allowing thefrequency selective surface to be used in close proximity to or incontact with (e.g., form part of a heat path, etc.) integrated circuits,other heat generating electronic components, heat sinks, etc. In anexemplary embodiment, a frequency selective surface includes thermallyconductive, electromagnetic energy absorptive composite materialavailable from Laird Technologies, Inc. and/or as disclosed in U.S. Pat.No. 7,608,326, the entire contents of which is incorporated herein.

In some exemplary embodiments, a single band or multiband bandstopwaveguide and/or shielding structure having a frequency selectivesurface may also be configured to exhibit or have thermally conductiveproperties. The substrate of the frequency selective surface may bethermally conductive, e.g., have a thermal conductivity of at least 0.5Watts per meter per Kelvin (W/mK) or more, have a thermal conductivitygreater than air, etc. In an exemplary embodiment, a frequency selectivesurface includes substrate comprising a composite material loaded withthermally conductive filler. In exemplary embodiments in which a singleband or multiband bandstop waveguide and/or shielding structure has orexhibits thermally conductive properties, the thermally conductiveproperties may enable the bandstop waveguide and/or shielding structureto be used in close proximity to or in contact with integrated circuits,other heat generating electronic components, heat sinks, etc. Forexample, a thermally conductive bandstop waveguide and/or shieldingstructure may be used adjacent or in contact with one or more heatgenerating components such that at least a portion of the thermallyconductive bandstop waveguide and/or shielding structure (e.g.,substrate or electrically-conductive members of the frequency selectivesurface, etc.) defines or includes part of a thermally conductive heatpath from the one or more heat generating components to a heat sink.

In some exemplary embodiments, the flexible structure of a frequencyselective surface may be incorporated in, integrated or integral with,applied, etc. on a surface, above, or inside a circuit board, such asafter the regular manufacturing process. The frequency selective surfacemay be conformable and/or heat cured over a board in some embodiments. Afrequency selective surface may be arranged normal to a board in aseries in some embodiments. By way of example, a frequency selectivesurface may be configured to be conformable to a mating surface and/orto have stiffness and flexibility properties similar to printed circuitboard substrates.

Advantageously, exemplary embodiments including frequency selectivesurfaces usable as single band or multiband bandstop waveguide and/orshielding structures disclosed herein may provide one or more (but notnecessarily any or all) of the following advantages. For example,exemplary embodiments may provide attenuation of electromagnetic signalsthrough open structures while allowing other objects and airflow throughthe open structures. A bandstop waveguide and/or shielding structure maybe positioned or installed within an open structure (e.g., opening, gap,channel, etc.) such that it is operable for attenuating electromagneticsignals or energy through the open structure without preventing accessto equipment or an airflow through the open structure. Accordingly, acooling airflow may flow through the open structure and/or equipment maybe accessed (e.g., for testing, repair, maintenance, replacement, etc.)via the open structure even while the bandstop waveguide and/orshielding structure remains installed or positioned within the openstructure. A tool or testing device may be inserted through the opening,gap, channel, or other open structure because the installed bandstopwaveguide and/or shielding structure does not completely block theopening, gap, channel, or other open structure. This is unlike someexisting traditional shielding or absorbing structures that operate bycompletely blocking the opening, gap, channel, or other open structurein which they are installed.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms, and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail. In addition, advantages and improvements that maybe achieved with one or more exemplary embodiments of the presentdisclosure are provided for purpose of illustration only and do notlimit the scope of the present disclosure, as exemplary embodimentsdisclosed herein may provide all or none of the above mentionedadvantages and improvements and still fall within the scope of thepresent disclosure.

Specific dimensions, specific materials, and/or specific shapesdisclosed herein are example in nature and do not limit the scope of thepresent disclosure. The disclosure herein of particular values andparticular ranges of values for given parameters are not exclusive ofother values and ranges of values that may be useful in one or more ofthe examples disclosed herein. Moreover, it is envisioned that anytwo-particular values for a specific parameter stated herein may definethe endpoints of a range of values that may be suitable for the givenparameter (i.e., the disclosure of a first value and a second value fora given parameter can be interpreted as disclosing that any valuebetween the first and second values could also be employed for the givenparameter). For example, if Parameter X is exemplified herein to havevalue A and also exemplified to have value Z, it is envisioned thatparameter X may have a range of values from about A to about Z.Similarly, it is envisioned that disclosure of two or more ranges ofvalues for a parameter (whether such ranges are nested, overlapping ordistinct) subsume all possible combination of ranges for the value thatmight be claimed using endpoints of the disclosed ranges. For example,if parameter X is exemplified herein to have values in the range of1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may haveother ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3,3-10, and 3-9.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

The term “about” when applied to values indicates that the calculationor the measurement allows some slight imprecision in the value (withsome approach to exactness in the value; approximately or reasonablyclose to the value; nearly). If, for some reason, the imprecisionprovided by “about” is not otherwise understood in the art with thisordinary meaning, then “about” as used herein indicates at leastvariations that may arise from ordinary methods of measuring or usingsuch parameters. For example, the terms “generally,” “about,” and“substantially,” may be used herein to mean within manufacturingtolerances. Or for example, the term “about” as used herein whenmodifying a quantity of an ingredient or reactant of the invention oremployed refers to variation in the numerical quantity that can happenthrough typical measuring and handling procedures used, for example,when making concentrates or solutions in the real world throughinadvertent error in these procedures; through differences in themanufacture, source, or purity of the ingredients employed to make thecompositions or carry out the methods; and the like. The term “about”also encompasses amounts that differ due to different equilibriumconditions for a composition resulting from a particular initialmixture. Whether or not modified by the term “about,” the claims includeequivalents to the quantities.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements, intended orstated uses, or features of a particular embodiment are generally notlimited to that particular embodiment, but, where applicable, areinterchangeable and can be used in a selected embodiment, even if notspecifically shown or described. The same may also be varied in manyways. Such variations are not to be regarded as a departure from thedisclosure, and all such modifications are intended to be includedwithin the scope of the disclosure.

1. A shielding structure comprising a frequency selective surfaceincluding at least a portion that is thermally conductive and/orconformable to a mating surface, whereby the frequency selective surfaceis operable for attenuating, reflecting, and/or redirectingelectromagnetic signals at one or more bandstop frequencies that arepropagating through a structure without completely blocking thestructure when the frequency selective surface is positioned withinstructure.
 2. The shielding structure of claim 1, wherein the frequencyselective surface is thermally conductive and conformable to a matingsurface.
 3. The shielding structure of claim 1, wherein the frequencyselective surface has a thermally conductivity of at least 0.5 Watts permeter Kelvin.
 4. The shielding structure of claim 1, wherein thefrequency selective surface comprises a substrate that is flexibleand/or thermally conductive.
 5. The shielding structure of claim 4,wherein: the substrate is thermally conductive and conformable to amating surface; and/or the substrate has a thermally conductivity of atleast 0.5 Watts per meter Kelvin.
 6. The shielding structure of claim 1,wherein the frequency selective surface comprises:electrically-conductive members; or electromagnetic energy absorptivemembers; or electrically-conductive, electromagnetic energy absorptivemembers; or electrically-conductive members and electromagnetic energyabsorptive members.
 7. The shielding structure of claim 1, wherein thefrequency selective surface comprises dielectric members andelectrically-conductive and/or electromagnetic energy absorptive memberson a substrate.
 8. The shielding structure of claim 1, wherein: theelectrically-conductive and/or electromagnetic energy absorptive memberscomprise electrically-conductive pressure sensitive adhesive; and/or thedielectric members comprise electrically non-conductive pressuresensitive adhesive or acrylonitrile butadiene styrene plastic; and/orthe substrate comprises acrylonitrile butadiene styrene plastic, Mylarplastic, or FR4 composite material including woven fiberglass cloth withan epoxy resin binder.
 9. The shielding structure of claim 1, wherein:the substrate comprises Mylar plastic; and the electrically-conductiveand/or electromagnetic energy absorptive members comprise copper etchedonto the Mylar plastic.
 10. The shielding structure of claim 1, whereinthe frequency selective surface comprises: electrically-conductiveand/or electromagnetic energy absorptive members; and dielectric membersconnected to and/or extending between corresponding pairs of theelectrically-conductive and/or electromagnetic energy absorptivemembers.
 11. The shielding structure of claim 10, wherein: theelectrically-conductive and/or electromagnetic energy absorptive memberscomprise circular rings; and the dielectric members comprise linearmembers each of which is connected between a corresponding pair of thecircular rings; and the electrically-conductive and/or electromagneticenergy absorptive members are at vertices of equilateral trianglesdefined by the dielectric members.
 12. The shielding structure of claim1, wherein the frequency selective surface compriseselectrically-conductive members and electromagnetic energy absorptivematerial applied to the electrically-conductive members, whereby theelectromagnetic energy absorptive material is operable for attenuatingthe electromagnetic signals reflected by the frequency selectivesurface.
 13. The shielding structure of claim 1, wherein the frequencyselective surface is tuned to have a bandstop frequency of about 9Gigahertz, whereby the frequency selective surface is operable forreflecting, blocking, redirecting, and/or absorbing energy having afrequency of about 9 Gigahertz propagating through an open structurewithout completely blocking the open structure when the frequencyselective surface is positioned within the open structure.
 14. Theshielding structure of claim 1, wherein the frequency selective surfacehas sufficient thermal conductivity for defining a thermally-conductiveheat path from one or more heat generating components when positionedfor providing shielding to the one or more heat generating components.15. The shielding structure of claim 1, wherein the frequency selectivesurface has sufficient flexibility for application to a part of a deviceafter manufacture of the part.
 16. A shielding structure comprising afrequency selective surface including electrically-conductive and/orelectromagnetic energy absorptive members and dielectric members,wherein the frequency selective surface is thermally conductive andconformable to a mating surface.
 17. The shielding structure of claim16, wherein the electrically-conductive and/or electromagnetic energyabsorptive members and dielectric members are on a substrate, andwherein: the electrically-conductive and/or electromagnetic energyabsorptive members comprise electrically-conductive pressure sensitiveadhesive, the dielectric members and the substrate compriseacrylonitrile butadiene styrene plastic; or the substrate comprisesMylar plastic, and the electrically-conductive and/or electromagneticenergy absorptive members comprise copper etched onto the Mylar plastic.18. The shielding structure of claim 16, wherein the frequency selectivesurface is operable for attenuating, reflecting, and/or redirectingelectromagnetic signals at one or more bandstop frequencies that arepropagating through a structure without completely blocking thestructure when the frequency selective surface is positioned within thestructure.
 19. A method comprising positioning a frequency selectivesurface relative to one or more electronic components such that thefrequency selective surface is operable for blocking electromagneticsignals at one or more bandstop frequencies, wherein at least a portionof the frequency selective surface is thermally conductive and/orconformable to a mating surface.
 20. The method of claim 19, wherein thefrequency selective surface includes electrically-conductive and/orelectromagnetic energy absorptive members and dielectric members on aflexible, thermally-conductive substrate.
 21. The method of claim 19,wherein positioning a frequency selective surface relative to one ormore electronic components comprises positioning the frequency selectivesurface within an open structure such that the frequency selectivesurface is operable for blocking electromagnetic signals at the one ormore bandstop frequencies that propagate through the open structurewithout completely blocking the open structure.
 22. The method of claim19, wherein positioning a frequency selective surface relative to one ormore electronic components comprises positioning the frequency selectivesurface to define a thermally-conductive heat path from the one or moreelectronic components to the frequency selective surface.
 23. The methodof claim 19, wherein positioning a frequency selective surface relativeto one or more electronic components comprises positioning the frequencyselective surface after manufacture of the one or more electroniccomponents.